A conventional hypodermic syringe includes a removable needle which is discarded along with the emptied glass anesthetic carpule after each use of the syringe. Once the needle is used, the needle poses a danger not only to the doctor or nurse handling the syringe, but anyone coming into contact with the needle. A variety of different types of devices have been provided for disposing of the needle and carpule such as various grinding machines for destroying and holding the discarded needle and carpule. Likewise, the various shields or containers have been provided into which the needle may be inserted prior to discarding. All of the devices, covers and shields heretofore provided require further handling of the needle from the point of patient use to the final destruction or storage. I have therefore devised a needle assembly which is operable together with the syringe plunger to withdraw the needle into the carpule upon completion of use of the syringe thereby completely isolating the needle immediately after the patient is injected and allowing the carpule to subsequently be discarded with the needle therein.